Catalysis-Based Fluorometric Method for Semiquantifying Trace Palladium in Sulfur-Containing Compounds and Ibuprofen

Trace palladium in synthetic materials can be rapidly and inexpensively semiquantified by a catalysis-based fluorometric method that converts resorufin allyl ether to resorufin. However, whether sulfur compounds would interfere with this method has not been systematically studied. Herein, we show that although thiourea in solution interferes with quantification, sulfide, thiol, and thiocarbamate do not. The fluorometric method can also detect palladium bound to sulfur-based scavenger resin and outperform inductively coupled plasma mass spectrometry for detecting trace palladium in ibuprofen.

Palladium nanoparticles for the synthesis of phenanthridinones and benzo[c]chromenes via C-H activation reaction

In the present work, derivatives of phenanthridine-6(5H)-ones and benzo[c]chromenes were efficiently prepared through an intramolecular C-H bond functionalization reaction catalyzed by photochemically synthesized Pd-PVP nanoparticles. The heterocycles were obtained via intramolecular arylation of the corresponding N-methyl-N-aryl-2-halobenzamide or aryl-(2-halo)benzyl ethers using K2CO3 as base in a mixture of H2O : DMA as solvent without additives or ligands. High yields of the heterocyclic compounds were achieved (up to 95%) using a moderately low catalyst loading (1-5 mol%) under an air atmosphere at 100 °C. The reaction exhibited very good tolerance to diverse functional groups (OMe, Me, t Bu, Ph, OCF3, CF3, F, Cl, -CN, Naph), and both bromine and iodine substrates showed great reactivity. Finally, the in vitro antiproliferative activity of phenanthridine-6(5H)-ones and benzo[c]chromenes was evaluated against six human solid tumor cell lines. The more active compounds exhibit activity in the low micromolar range. 1-Isopropyl-4-methyl-6H-benzo[c]chromene was identified as the best compound with promising values of activity (GI50 range 3.9-8.6 μM). Thus, the benzochromene core was highlighted as a novel organic building block to prepare potential antitumor agents.

Pd Nanoparticle-Catalyzed Stereospecific Mizoroki-Heck Arylation of cis-1,2-Disilylarylethylenes

In the presence of catalytic amounts of Pd nanoparticles, generated from Pd2dba3/Ag(I), cis-1,2-ditrimethylsilylarylethylenes undergo with aryl iodides a stereospecific Mizoroki-Heck arylation leading to trans-ditrimethylsilyldiarylethylenes. This chemoselectivity is in contrast to that of their trimethylgermyl analogues, which are arylated at the position of the C-Ge bonds. trans-1,2-Ditrimethylsilylarylethylenes are completely unreactive under the standard reaction conditions. The reaction tolerates the presence of boryl, silyl, or bromine substituents on the aryl iodides. From a mechanistic point of view, the process involves syn-arylpalladation followed by syn-dehydropalladation.

TiO2-Modified Montmorillonite-Supported Porous Carbon-Immobilized Pd Species Nanocomposite as an Efficient Catalyst for Sonogashira Reactions

In this study, a combination of the porous carbon (PCN), montmorillonite (MMT), and TiO₂ was synthesized into a composite immobilized Pd metal catalyst (TiO₂-MMT/PCN@Pd) with effective synergism improvements in catalytic performance. The successful TiO₂-pillaring modification for MMT, derivation of carbon from the biopolymer of chitosan, and immobilization of Pd species for the prepared TiO₂-MMT/PCN@Pd⁰ nanocomposites were confirmed using a combined characterization with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption-desorption isotherms, high-resolution transition electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It was shown that the combination of PCN, MMT, and TiO₂ as a composite support for the stabilization of the Pd catalysts could synergistically improve the adsorption and catalytic properties. The resultant TiO₂-MMT₈₀/PCN₂₀@Pd⁰ showed a high surface area of 108.9 m²/g. Furthermore, it exhibited moderate to excellent activity (59-99% yield) and high stability (recyclable 19 times) in the liquid-solid catalytic reactions, such as the Sonogashira reactions of aryl halides (I, Br) with terminal alkynes in organic solutions. The positron annihilation lifetime spectroscopy (PALS) characterization sensitively detected the development of sub-nanoscale microdefects in the catalyst after long-term recycling service. This study provided direct evidence for the formation of some larger-sized microdefects during sequential recycling, which would act as leaching channels for loaded molecules, including active Pd species.

Mechanically Robust Hybrid Gel Beads Loaded with "Naked" Palladium Nanoparticles as Efficient, Reusable, and Sustainable Catalysts for the Suzuki-Miyaura Reaction

The increase in demand for Pd and its low abundance pose a significant threat to its future availability, rendering research into more sustainable Pd-based technologies essential. Herein, we report Pd scavenging mechanically robust hybrid gel beads composed of agarose, a polymer gelator (PG), and an active low-molecular-weight gelator (LMWG) based on 1,3:2,4-dibenzylidenesorbitol (DBS), DBS-CONHNH ₂ . The robustness of the PG and the ability of the LMWG to reduce Pd(II) in situ to generate naked Pd(0) nanoparticles (PdNPs) combine within these gel beads to give them potential as practical catalysts for Suzuki-Miyaura cross-coupling reactions. The optimized gel beads demonstrate good reusability, green metrics, and most importantly the ability to sustain stirring, improving reaction times and energy consumption compared to previous examples. In contrast to previous reports, the leaching of palladium from these next-generation beads is almost completely eliminated. Additionally, for the first time, a detailed investigation of these Pd-loaded gel beads explains precisely how the nanoparticles are formed in situ without a stabilizing ligand. Further, detailed catalytic investigations demonstrate that catalysis occurs within the gel beads. Hence, these beads can essentially be considered as robust "nonligated" heterogeneous PdNP catalysts. Given the challenges in developing ligand-free, naked Pd nanoparticles as stable catalysts, these gel beads may have future potential for the development of easily used systems to perform chemical reactions in "kit" form.

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

Recent developments in C–C bond formation catalyzed by solid supported palladium: a greener perspective

The world today is struggling to achieve sustainable means for synthetic processes. Standing at this juncture, we need to develop and implement greener and reusable approaches towards organic synthesis. Transition metals especially palladium is a wonder element which has the ability to catalyze a range of useful organic syntheses. However, the expensive nature of palladium has urged synthetic chemists to search for protocols where a single palladium source may be used repeatedly in successive reactions, thus making the overall process cost effective. Palladium when anchored to solid supports leads to catalytic systems which can be easily separated from the organic phase post reaction and can be reused in successive cycles. Not only does this make the process economically viable but also ensures that no metal contaminates the purity of the final organic product. In this review we will highlight the recent developments in C–C bond formation (which is by far the most fundamental mode of bond making in organic synthesis) via the use of solid supported palladium catalytic systems. We will use this opportunity to illustrate the synthetic processes from a greener sustainable point of view which we feel is of utmost relevance in the current scientific scenario.

Synthesis of Unsymmetrical Biheteroarenes via Dehydrogenative and Decarboxylative Coupling: a Decade Update

The design and development of robust and efficient methods for installing one heterocycle with another is endowed as a ubiquitous and powerful synthetic strategy to access complex organic biheterocycles in recent days due to their pervasive applications in medicinal as well as material chemistry. This perspective presents an overview on the recent findings and developments for the synthesis of unsymmetrical biheteroarenes via dehydrogenative and decarboxylative couplings with literature coverage mainly extending from 2011 to 2021. For simplification of the readers, the article has been subcategorized based on the catalysts used in the reactions.

Green Synthesis of Pd Nanoparticles for Sustainable and Environmentally Benign Processes

Among transition metal nanoparticles, palladium nanoparticles (PdNPs) are recognized for their high catalytic activity in a wide range of organic transformations that are of academic and industrial importance. The increased interest in environmental issues has led to the development of various green approaches for the preparation of efficient, low-cost and environmentally sustainable Pd-nanocatalysts. Environmentally friendly solvents, non-toxic reducing reagents, biodegradable capping and stabilizing agents and energy-efficient synthetic methods are the main aspects that have been taken into account for the production of Pd nanoparticles in a green approach. This review provides an overview of the fundamental approaches used for the green synthesis of PdNPs and their catalytic application in sustainable processes as cross-coupling reactions and reductions with particular attention afforded to the recovery and reuse of the palladium nanocatalyst, from 2015 to the present.

Facile Synthesis and Characterization of Palladium@Carbon Catalyst for the Suzuki-Miyaura and Mizoroki-Heck Coupling Reactions

Palladium-based carbon catalysts (Pd/C) can be potentially applied as an efficient catalyst for Suzuki–Miyaura and Mizoroki–Heck coupling reactions. Herein, a variety of catalysts of palladium on activated carbon were prepared by varying the content of ‘Pd’ via an in situ reduction method, using hydrogen as a reducing agent. The as-prepared catalysts (0.5 wt % Pd/C, 1 wt % Pd/C, 2 wt % Pd/C and 3 wt % Pd/C) were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Brunauer–Emmett–Teller (BET) analyses. The catalysts were tested as a coupling catalyst for Suzuki–Miyaura coupling reactions involving aryl halides and phenyl boronic acid. The optimization of the catalyst by varying the palladium content on the activated carbon yielded Pd/C catalysts with very high catalytic activity for Suzuki reactions of aryl halides and a Mizoroki–Heck cross-coupling reaction of 4-bromoanisol and acrylic acid in an aqueous medium. A high ‘Pd’ content and uniform ‘Pd’ impregnation significantly affected the activity of the catalysts. The catalytic activity of 3% Pd/C was found to make it a more efficient catalyst when compared with the other synthesized Pd/C catalysts. Furthermore, the catalyst reusability was also tested for Suzuki reactions by repeatedly performing the same reaction using the recovered catalyst. The 3% Pd/C catalyst displayed better reusability even after several reactions.

Design of Glycerol-Based Solvents for the Immobilization of Palladium Nanocatalysts: A Hydrogenation Study

Twenty-one green solvents, including glycerol-derived ethers, and their eutectic mixtures with two renewable ammonium salts, were used for the straightforward synthesis, stabilization, and immobilization of palladium nanoparticles (Pd NPs). The nature of the solvent allows tuning of the characteristics and properties of resulting catalytic systems in terms of particle size and morphology, stability, reactivity, and recoverability. Pd NPs immobilized in glycerol-based solvents were applied in the catalytic hydrogenation of alkenes, alkynes, and carbonyl compounds, as well as in the selective semihydrogenation of alkynes to alkenes. The optimal experimental parameters and the influence on the reactivity of the physicochemical properties of solvent, mainly the viscosity, were studied. Moreover, the most active and recoverable catalytic system, Pd NPs/N00Cl-100, was fully characterized both in the liquid phase and in the solid state, and its deactivation upon recovery was analyzed.

A Bis (BICAAC) Palladium(II) Complex: Synthesis and Implementation as Catalyst in Heck-Mizoroki and Suzuki-Miyaura Cross Coupling Reactions

Carbenes are one of the most appealing, well-explored, and exciting ligands in modern chemistry due to their tunable stereoelectronic properties and a wide area of applications. A palladium complex (BICAAC)₂PdCl₂ with a recently discovered cyclic (alkyl)(amino)carbene having bicyclo[2.2.2] octane skeleton (BICAAC) was synthesized and characterized. The enhanced σ-donating and π-accepting ability of this carbene lend a hand to form a robust Pd-carbene bond, which allowed us to probe its reactivity as a precatalyst in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions with low catalyst loading in open-air conditions. The diverse range of substrates was explored for both the cross-coupling reactions. To get a better understanding of the catalytic reactions, several analytical techniques such as field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and powder X-ray diffraction were employed in a conclusive manner.

A magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdII nanocomposite exhibiting facile tandem Suzuki coupling/transfer hydrogenation reaction

Herein, we report a magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdIINP (5) nanocomposite system for tandem Suzuki coupling/transfer hydrogenation reaction. The nanocomposite 5 was prepared first by making a layer of [Formula: see text] on [Formula: see text] followed by deposition of [Formula: see text] and sorption of [Formula: see text] ions successively onto the surface of Fe3O4@SiO2NP. The nanocomposite was characterized by powder XRD, electron microscopy (SEM-EDS and TEM-EDS) and XPS spectroscopy techniques. The mixed-valent [Formula: see text] present onto the surface of nanocomposite 5 was confirmed by XPS technique. Interestingly, the mixed-valent nanocomposite Fe3O4@SiO2/Pd0/PdIINP (5) exhibited tandem Suzuki coupling/transfer hydrogenation reaction during the reaction of aryl bromide with aryl boronic acid (90% of C). The nanocomposite 5 displayed much better reactivity as compared to the monovalent Fe3O4@SiO2/Pd0NP (3) (25% of C) and Fe3O4@SiO2/PdIINP (4) (15% of C) nanocomposites. Further, because of the presence of magnetic [Formula: see text], the nanocomposite displayed its facile separation from the reaction mixture and reused at least for five catalytic cycles.

Prospects and Applications of Palladium Nanoparticles in the Cross-coupling of (hetero)aryl Halides and Related Analogues

Discovering efficient methods for the formation of carbon-carbon bonds is a central ongoing theme in organic synthesis. Cross-coupling reactions catalysed by metal nanoparticles are attractive alternatives to the traditional use of metal counterparts due to the catalytic tunability, selectivity, recyclability and reusability of the nanoparticles. The ongoing search for sustainable processes demands that reusable and environmentally benign catalysts are used. While the advantages of nanoparticles catalysts over bulk catalysts cannot be overemphasised, the problem of sintering, agglomeration and leaching are drawbacks to their full industrial applications. Hence, efforts are being made towards advancing the efficiency of the catalytic nanoparticle systems over the years. This review presents the progress, the challenges and the prospects of palladium nanoparticle with focus on Heck, Suzuki, Hiyama and Sonogashira cross-coupling reactions involving (hetero) aryl halides and the analogues.

Comparative study of aryl halides in Pd-mediated reactions: key factors beyond the oxidative addition step

The comparative experimental study of Ar–X (X = Cl, Br, I) reactivity and analysis reported herein suggest that oxidative addition cannot be considered the sole reason of the observed low reactivity of aryl chlorides.

Nanoengineering with RAFT polymers: from nanocomposite design to applications

Reversible addition–fragmentation chain-transfer (RAFT) polymerization is a powerful tool for the precise formation of macromolecular building blocks that can be used for the construction of well-defined nanocomposites.

Palladium nanoparticles in situ synthesized on Cyclea barbata pectin as a heterogeneous catalyst for Heck coupling in water, the reduction of nitrophenols and alkynes

This study develops an effective method for in situ synthesis of PdNPs using Cyclea barbata pectin as green reducing and stabilizing reagent. The catalytic activity of nanocomposite was evaluated for Heck coupling reaction, reduction of nitrophenols and reduction of alkynes.

Efficient recovery of palladium nanoparticles from industrial wastewater and their catalytic activity toward reduction of 4-nitrophenol

Discharge of heavy metals from various sources of industrial wastewater poses significant environmental and health concerns. Thus, efficient recovery of precious metals from wastewater employing sustainable, rapid, and cost-effective treatment methods is highly desirable. In this work, palladium nanoparticles (Pd NPs) were successfully recovered from industrial wastewater using a pulsed laser process in the absence of additives or reducing agents. Notably, the developed approach is faster and more environmentally friendly than other conventional recovery methods. The recovered Pd NPs were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Various pulsed laser parameters (i.e., laser wavelength, power, and irradiation time) were optimized to obtain ideal conditions for the pulsed laser ablation process. Effective recovery of the Pd metal from industrial wastewater was achieved at a laser wavelength of 355 nm, power of 40 mJ/pulse, and irradiation time of 30 min. The Pd NPs exhibited excellent catalytic activity toward the reduction of 4-nitrophenol. Thus, the recovered materials showed remarkable potential for application in degradation of toxic aromatic nitro compounds in the environment.

α, β-Alkynone Accelerated PPM Level Pd-Catalyzed Sonogashira Coupling Reaction

In the palladium-catalyzed C−C coupling reaction, electron-rich phosphine ligands and a catalytic amount of catalyst loading are required in most cases. Herein, a bench-stable, easily modified and less toxic alkynone was utilized in palladium-catalyzed Sonogashira coupling to replace conventional phosphine ligands. With 1-(4-methoxyphenyl)-3-phenyl-2-yn-1-one (L2) as the ligand, catalyst loading was reduced to 5-10 ppm. In this newly developed catalytic system, a variety of (hetero)arene iodines and alkynes could be tolerated, resulting in good yields of the corresponding cross-coupling products.

Palladium Oxide Nanoparticles: Preparation, Characterization and Catalytic Activity Evaluation

Stable palladium oxide nanoparticles were prepared in aqueous suspension with a very simple procedure, by dissolving palladium nitrate in water at a concentration around 10−4 M. UV-visible absorption spectroscopy was adopted to follow the formation of these nanoparticles, which were characterized by TEM microscopy, along with XRD, XPS and Raman measurements. DFT calculations allowed to interpret the Raman data and to clarify the species present at the surface of the nanoparticles. The catalytic activity of the latter was evaluated by monitoring the reduction of p-nitrophenol to p-aminophenol. This investigation paves the way to the use of these colloidal nanoparticles in processes of heterogeneous catalysis, in particular those concerning the catalytic degradation of aromatic derivatives that represent a serious danger for the environment as pollutants, as in the case of p-nitrophenol.

Strategy used to synthesize high activity and low Pd catalyst for Suzuki coupling reaction: an experimental and theoretical investigation

Compared with Pd₁₄₇ DEN, Pd₇₄Cu₇₃ DEN shows comparable catalytic performance, with TOFs of 8519 and 8728 h⁻¹, and provides a valuable strategy for designing a low Pd dosage and high-activity catalyst for Suzuki coupling.

Pd nanoparticles stabilized with phosphine-functionalized porous ionic polymer for efficient catalytic hydrogenation of nitroarenes in water

Small palladium nanoparticles stabilized with phosphine-functionalized PIP displayed high catalytic activity for nitroarenes hydrogenation. Nano-size Pd particles, electron-donation effect of phosphine ligand, and surface wettability account for its excellent catalytic performance.

Palladium nanoparticles as efficient catalyst for C–S bond formation reactions

Heterogenous catalysis: economical and sustainable synthesis of allylic sulfone featuring tri- and even tetrasubstituted olefin scaffold via decarboxylative cross-coupling from vinyl cyclic carbonates with sodium sulfinates using PdNPs as a catalyst.

High Catalytic Activity of Pd Nanoparticles Synthesized from Green Alga Chlorella vulgaris in Buchwald-hartwig Synthesis of N-Aryl Piperazines

Background:

The N-aryl piperazines are an important component of many drug products used for the treatment of malaria, depression, anxiety and Parkinson diseases. Buchwald-Hartwig amination is the latest and well-known reaction for Pd catalyzed direct synthesis of N-aryl piperazine from aryl halides. Although several Pd-ligand systems have already been discovered for this conversion, Pd nanoparticles are recently being used for this useful coupling reaction due to their recyclability and durability. Metal nanoparticles show enhanced catalytic activity compared to their bulk counterparts due to increased surface area at the edges and corners. The use of green algal extract in place of chemical ligands makes this process more environment-friendly and cost-effective. In this research, Pd nanoparticles synthesized using green alga C. Vulgaris were utilized as an alternative approach for the coupling reaction during the preparation of N-aryl piperazines.

Methods:

Synthesized Pd nanoparticles from C. Vulgaris were characterized by FTIR, SEM and XRD techniques. The catalytic activity of the synthesized nanoparticles was monitored for the synthesis of N-aryl piperazines by Buchwald-Hartwig reaction. The synthesized N-aryl piperazines were characterized by NMR, FTIR and mass analysis.

Results:

A very good catalytic activity of the synthesized Pd nanoparticles from green alga Chlorella vulgaris extract was observed. The green alga not only reduces the size of the Pd metal to nanoparticles but also acts as a green ligand for reduction of Pd(II) to Pd(0) during nanoparticle synthesis. Using this Pd nanoparticles-green ligand system, several N-aryl piperazines were synthesized in good to excellent yields. Reaction conditions for better conversion were optimized. The comparative advantage of the catalytic system with recently published works on Buchwald-Hartwig C-N coupling reaction is given. Recyclability and durability of the catalyst were explored and the results were found to be promising. A plausible mechanism of Pd nanoparticle catalyzed reaction is also proposed.

Conclusion:

Catalytic activity of the Pd nanoparticle synthesized from Chlorella vulagris in the synthesis of N-aryl piperazines by Buchwald-Hartwig reaction is reported first time to the best of our knowledge and understanding. The green approach of Pd catalyst to facilitate the reaction and its environmental impact is the main characteristic of the process.

Synthesis, growth mechanisms, and applications of palladium-based nanowires and other one-dimensional nanostructures

Palladium-based nanostructures have attracted the attention of researchers due to their useful catalytic properties and unique ability to form hydrides, which finds application in hydrogen storage and hydrogen detection. Palladium-based nanowires have some inherent advantages over other Pd nanomaterials, combining high surface-to-volume ratio with good thermal and electron transport properties, and exposing high-index crystal facets that can have enhanced catalytic activity. Over the past two decades, both synthesis methods and applications of 1D palladium nanostructures have advanced greatly. In this review, we start by discussing different types of 1D palladium nanostructures before moving on to the different synthesis approaches that can produce them. Next, we discuss factors including kinetic vs. thermodynamic control of growth, oxidative etching, and surface passivation that affect palladium nanowire synthesis. We also review efforts to gain insight into growth mechanisms using different characterization tools. We discuss the effects of concentration of capping agents, reducing agents, metal halides, pH, and sacrificial oxidation on the growth of Pd-based nanowires in solution, from shape control, to yield, to aspect ratio. Various applications of palladium and palladium alloy nanowires are then discussed, including electrocatalysis, hydrogen storage, and sensing of hydrogen and other chemicals. We conclude with a summary and some perspectives on future research directions for this category of nanomaterials.

Metal Nanoparticles: An Efficient Tool for Heterocycles Synthesis and Their Functionalization via C-H Activation

Background:

Metal nanoparticles have been extensively used in the synthesis of organic molecules during the last few decades especially due to their high catalytic activity. Organic reactions involving C-H functionalisations are very much in demand as they provide a direct method of derivatisation of organic molecules, thus making the process economical. In the recent years, metal nanoparticles catalysed C-H activation reactions have led to the design of useful molecules especially heterocyclic motifs which form the core structure of drugs and thus have high biological and industrial importance.

Methods:

In this review, we present a collection of reactions where metal nanoparticles are instrumental in the synthesis and functionalization of heterocycles via C-H activation. The review consists of three units namely, Nano-copper catalysed C-H activation reactions, nano-palladium catalysed CH activation reactions and other nano-metals catalysed C-H activation reactions.

Results:

The discussion reflects the scope of nano-metals as effective catalysts for the synthesis and functionalization of heterocycles as well as the efficiency of nano-metals towards catalysing economic and environmentally viable reaction protocols.

Conclusion:

The theme of this review is to correlate nanometal catalysis, heterocyclic synthesis and C-H activation, each of which in itself forms an integral part of modern day chemical research. Thus, the review will hopefully highlight the need for future development and research in this area and be instrumental in guiding researchers towards fulfilling that goal.

Disconnecting Symmetry Breaking from Seeded Growth for the Reproducible Synthesis of High Quality Gold Nanorods

One of the major difficulties hindering the widespread application of colloidal anisotropic plasmonic nanoparticles is the limited robustness and reproducibility of multistep synthetic methods. We demonstrate herein that the reproducibility and reliability of colloidal gold nanorod (AuNR) synthesis can be greatly improved by disconnecting the symmetry-breaking event from the seeded growth process. We have used a modified silver-assisted seeded growth method in the presence of the surfactant hexadecyltrimethylammonium bromide and n-decanol as a co-surfactant to prepare small AuNRs in high yield, which were then used as seeds for the growth of high quality AuNR colloids. Whereas the use of n-decanol provides a more-rigid micellar system, the growth on anisotropic seeds avoids sources of irreproducibility during the symmetry breaking step, yielding uniform AuNR colloids with narrow plasmon bands, ranging from 600 to 1270 nm, and allowing the fine-tuning of the final dimensions. This method provides a robust route for the preparation of high quality AuNR colloids with tunable morphology, size, and optical response in a reproducible and scalable manner.